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Kondo, Yosuke*; Achouri, N. L.*; Al Falou, H.*; Atar, L.*; Aumann, T.*; Baba, Hidetada*; Boretzky, K.*; Caesar, C.*; Calvet, D.*; Chae, H.*; et al.
Nature, 620(7976), p.965 - 970, 2023/08
Times Cited Count:5 Percentile:92.64(Multidisciplinary Sciences)no abstracts in English
Wang, H.*; Yasuda, Masahiro*; Kondo, Yosuke*; Nakamura, Takashi*; Tostevin, J. A.*; Ogata, Kazuyuki*; Otsuka, Takaharu*; Poves, A.*; Shimizu, Noritaka*; Yoshida, Kazuki; et al.
Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08
Times Cited Count:2 Percentile:68.16(Astronomy & Astrophysics)Detailed -ray spectroscopy of the exotic neon isotope Ne has been performed using the one-neutron removal reaction from Ne. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.
Tanaka, Taiki*; Narikiyo, Yoshihiro*; Morita, Kosuke*; Fujita, Kunihiro*; Kaji, Daiya*; Morimoto, Koji*; Yamaki, Sayaka*; Wakabayashi, Yasuo*; Tanaka, Kengo*; Takeyama, Mirei*; et al.
Journal of the Physical Society of Japan, 87(1), p.014201_1 - 014201_9, 2018/01
Times Cited Count:18 Percentile:74.47(Physics, Multidisciplinary)Excitation functions of quasielastic scattering cross sections for the Ca + Pb, Ti + Pb, and Ca + Cm reactions were successfully measured by using the gas-filled recoil-ion separator GARIS. Fusion barrier distributions were extracted from these data, and compared with the coupled-channels calculations. It was found that the peak energies of the barrier distributions for the Ca + Pb and Ti + Pb systems coincide with those of the 2n evaporation channel cross sections for the systems, while that of the Ca + Cm is located slightly below the 4n evaporation ones. This results provide us helpful information to predict the optimum beam energy to synthesize superheavy nuclei.
Torigoe, Shuhei*; Ishimoto, Yutaro*; Aoishi, Yuhei*; Murakawa, Hiroshi*; Matsumura, Daiju; Yoshii, Kenji; Yoneda, Yasuhiro; Nishihata, Yasuo; Kodama, Katsuaki; Tomiyasu, Keisuke*; et al.
Physical Review B, 93(8), p.085109_1 - 085109_5, 2016/02
Times Cited Count:5 Percentile:25.9(Materials Science, Multidisciplinary)Yoshii, Kenji; Yoneda, Yasuhiro; Jarrige, I.*; Fukuda, Tatsuo; Nishihata, Yasuo; Suzuki, Chikashi; Ito, Yoshiaki*; Terashima, Takahito*; Yoshikado, Shinzo*; Fukushima, Sei*
Journal of Physics and Chemistry of Solids, 75(3), p.339 - 343, 2014/03
Times Cited Count:10 Percentile:41.9(Chemistry, Multidisciplinary)We have studied the electronic properties of ferroelectric BaTiO using two complementary bulk-sensitive spectroscopic probes, resonant X-ray emission spectroscopy (RXES) and X-ray absorption spectroscopy in the partial fluorescence mode (PFY-XAS). Contrary to a previous study, we found no temperature change of a PFY-XAS spectrum at the Ba L edge between room temperature and 150C. This result is not supportive of the possible presence of the displacement around Ba at the Curie temperature. RXES spectra were measured at the Ti K edge for BaTiO, along with SrTiO and La-doped metallic SrTiO. The photon energy of the emission peak is found to be nearly constant throughout the absorption edge for all three compounds. We deduce the Ti 3d states to have a delocalized character, in contrast with the Ba 5d states, a property which is consistent with the proposed scenario of the formation of electric dipoles in BaTiO.
Yoshii, Kenji; Ikeda, Naoshi*; Fukuyama, Ryota*; Nagata, Tomoko*; Kambe, Takashi*; Yoneda, Yasuhiro; Fukuda, Tatsuo; Mori, Shigeo*
Solid State Communications, 173, p.34 - 37, 2013/11
Times Cited Count:4 Percentile:20.56(Physics, Condensed Matter)We have investigated the magnetic properties of RFeO (R=Yb and Lu), which belongs to the homologous family of electronic ferroelectric RFeO. Magnetization measurements show ferrimagnetic ordering at the Neel temperature (T) of about 270 K, which is slightly higher than that of RFeO (T about 230-250 K). Observation of spin glass and exchange bias shows a coexistence of ferromagnetic and antiferromagneticinteractions, similarly to RFeO. This situation gives rise to a complex magnetic change and a broad peak of magnetic entropy change. Some characteristics, such as refrigeration temperatures higher than in RFeO, seem to offer a possibility of this system to applications.
Yoneda, Yasuhiro; Yoshii, Kenji; Suzuki, Chikashi
Transactions of the Materials Research Society of Japan, 37(4), p.579 - 582, 2012/12
We performed X-ray Emission spectroscopy (XES) by using a double crystal spectrometer. Ta-L and L emission lines of Ta-related materials of Ta-metal, TaO, LiTaO, and KTaO were measured. XES is one of the most important spectroscopies to make a remarkable progress utilizing third generation synchrotron radiation sources. Here, I discuss some aspects of XES in Ta compounds of recent experimental data. We also discuss an azimuth dependence of resonant X-ray emission spectra (RXES) of a single-crystal KTaO. The precise measurement by the double crystal spectrometer has observed change of the electronic structure by crystal orientation. Since electronic structure observation is a local probe, it can detect minute lattice deformation.
Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sumita, Takayuki*; Wakabayashi, Yasuo*; Yoneda, Akira*; Tanaka, Kengo*; et al.
Journal of the Physical Society of Japan, 81(10), p.103201_1 - 103201_4, 2012/10
Times Cited Count:167 Percentile:97.27(Physics, Multidisciplinary)An isotope of the 113th element, 113, was produced in a nuclear reaction with a Zn beam on a Bi target. We observed six consecutive decays following the implantation of a heavy particle in nearly the same position in the semiconductor detector, in extremely low background condition. The fifth and sixth decays are fully consistent with the sequential decays of Db and Lr both in decay energies and decay times. This indicates that the present decay chain consisted of 113, Rg (Z = 111), Mt (Z = 109), Bh (Z = 107), Db (Z = 105), and Lr (Z = 103) with firm connections. This result, together with previously reported results from 2004 and 2007, conclusively leads the unambiguous production and identification of the isotope 113, of the 113th element.
Yoshii, Kenji; Jarrige, I.; Suzuki, Chikashi; Matsumura, Daiju; Nishihata, Yasuo; Yoneda, Yasuhiro; Fukuda, Tatsuo; Tamura, Kazuhisa; Ito, Yoshiaki*; Mukoyama, Takeshi*; et al.
Journal of Physics and Chemistry of Solids, 73(9), p.1106 - 1110, 2012/09
Times Cited Count:11 Percentile:44.07(Chemistry, Multidisciplinary)We have directly probed the Ba 5d states in the ferroelectric barium titanate BaTiO using resonant X-ray emission spectroscopy (RXES) and X-ray absorption spectroscopy in the partial fluorescence mode (PFY-XAS) at the Ba-L edge. The results are compared with those of the non-ferroelectric BaSO. While the RXES spectra point to a localized character for the Ba 5d states in both compounds, the main peak of the PFY-XAS spectrum, corresponding to the dipolar transitions from 2p to 5d, is found to be significantly broader for BaTiO than for BaSO. On the basis of band structure calculations, this broadening is ascribed to strong hybridization between the unoccupied Ba 5d and O 2p states in the ferroelectric. This suggests that the hybridization between the conduction states of the Ba and O ions, and not only Ti and O, plays a central role in determining the electronic structure of BaTiO.
Yoneda, Yasuhiro; Yoshii, Kenji; Kohara, Shinji*
Transactions of the Materials Research Society of Japan, 37(1), p.73 - 76, 2012/03
The structures and phase transitions of AgNbO were investigated using high-energy X-ray powder diffraction. Bragg reflections have revealed the high temperature M-O, O-T, and T-C phase transitions but have not given any significant evidence of low temperature M-M and M-M ones. The existence of structural disorder in the T and O phases was indicated by diffuse scattering. Here we again confirm the average structure of AgNbO. The refined structure was essentially the same as previous reports. With isotropic thermal parameters, refinements of the structures at most temperatures resulted in larger Ag thermal parameters. Disorder feature of Ag coupled with the thermal parameters and exhibit as diffuse scattering in T and O phases.
Yoneda, Yasuhiro; Saito, Hiroyuki; Yoshii, Kenji
Japanese Journal of Applied Physics, 50(9), p.09NE06_1 - 09NE06_6, 2011/09
Times Cited Count:13 Percentile:49.19(Physics, Applied)Bi(MgTi)O (BMT) was grown by high-pressure and high-temperature synthesis to achieve the morphotropic phase boundary induced by pressure. Two types of BMT was obtained; one has orthorhombic structure and the other has rhombohedral structure. high-pressure and high-temperature X-ray diffraction measurements were performed, and it clarified that the orthorhombic structure is stabilized in the ambient pressure phase and the rhombohedral structure is stabilized in the high pressure phase. We also performed local structure analysis by using pair-distribution function analysis. The similarity of local structures in the orthorhombic and rhombohedral BMT was revealed, and it was also the phase transition mechanism to the high-pressure rhombohedral phase.
Torigoe, Shuhei*; Ishimoto, Yutaro*; Hanasaki, Noriaki*; Nogami, Yoshio*; Matsumura, Daiju; Yoshii, Kenji; Yoneda, Yasuhiro; Nishihata, Yasuo
Journal of Physics; Conference Series, 320, p.012078_1 - 012078_4, 2011/09
Times Cited Count:1 Percentile:33.9(Physics, Condensed Matter)The X-ray absorption spectra of some pyrochlore niobates reveal the valence of the Nb ion in each material, and the displacement of the Nb ions from the center of the oxygen octahedra in the pyrochlore niobates YCaNbO and NdCaNbO, which is consistent with the previous report of the neutron diffraction.
Yoshii, Kenji; Hiramitsu, Yusuke*; Okajima, Yuka*; Yoneda, Yasuhiro; Nishihata, Yasuo; Mizuki, Junichiro; Nakamura, Akio; Shimojo, Yutaka; Ishii, Yoshinobu*; Morii, Yukio; et al.
Materials Research Bulletin, 45(11), p.1574 - 1580, 2010/10
Times Cited Count:12 Percentile:37.22(Materials Science, Multidisciplinary)Magnetic and dielectric properties of perovskite manganites RSrMnO (R = Gd, Tb and Dy) have been investigated. DC and AC magnetic measurements showed short-range glassy magnetic ordering at Tg about 40 K. Such ordering was observed by neutron diffraction and is ascribable to the size mismatch of R and Sr settled randomly at the same crystallographic site. Dielectric constants for each material were about 1000-10000 between about 50 K and 300 K and showed broad maximums above Tg. Dielectric dispersion showed poor coherency of the motion of polar regions, plausibly because of the size-mismatch effect; both the magnetic and dielectric properties of this system are governed by the randomness at the R/Sr site. The tan and EXAFS data suggest that the dielectric response is rooted in a transfer of the Mn-3d electrons.
Yoneda, Yasuhiro; Saito, Hiroyuki; Yoshii, Kenji; Nishida, Takashi*; Hayakawa, Hironori*; Ikeda, Naoshi*
Key Engineering Materials, 421-422, p.30 - 33, 2010/00
Polycrystalline Bi(MgTi)O samples were prepared under high pressure. A mixed powder of BiO, TiO and MgO with a prescribed ratio was packed into platinum cell and was heated a cubic anvil-type apparatus at 6.5 GPa and 1000 C. The obtained samples were characterized by powder X-ray diffraction measurements. Although some impurity peaks existed, the main peaks were perovskite peaks. The structure of Bi(MgTi)O is rhombohedral, as well as BiFeO. The D-E hysteresis loop was not saturated due to the impurities, but the possibility as ferroelectric can be expected enough.
Yoshii, Kenji; Ikeda, Naoshi*; Michiuchi, Takamasa*; Yokota, Yusuke*; Okajima, Yuka; Yoneda, Yasuhiro; Matsuo, Yoji*; Horibe, Yoichi*; Mori, Shigeo*
Journal of Solid State Chemistry, 182(7), p.1611 - 1618, 2009/06
Times Cited Count:15 Percentile:51.45(Chemistry, Inorganic & Nuclear)We have investigated the magnetic and dielectric properties of YbFeMnO (0x1), which is an Fe-site-substituted system of new multiferroic oxides RFeO (R=Y, Ho-Lu). X-ray diffraction measurements show that a solid solution is formed between YbFeO (x=0) and YbFeMnO (x=1) for 0x1. The valence of the Mn ion is determined to be 2+, consistently with the suppression of low-temperature magnetization by the Mn substitution. The magnetic transition temperature and the dielectric constant decrease monotonically with increasing x. This result plausibly confirms that the magnetic and dielectric properties in oxides isostructural with RFeO are governed by the electron transfer between Fe-site ions, unlike ordinary ferroelectrics and dielectrics, in which the ionic displacement plays a key role. The possibility for application is briefly discussed.
Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sato, Nozomi*; Sumita, Takayuki*; Yoneda, Akira*; Ichikawa, Takatoshi*; et al.
Journal of the Physical Society of Japan, 78(6), p.064201_1 - 064201_6, 2009/06
Times Cited Count:30 Percentile:78.34(Physics, Multidisciplinary)Decay properties of an isotope Bh and its daughter nucleus Db produced by the Cm(Na,5) reaction were studied by using a gas-filled recoil separator coupled with a position-sensitive semiconductor detector. Bh was clearly identified from the correlation of the known nuclide, Db. The obtained decay properties of Bh and Db are consistent with those observed in the 113 chain, which provided further confirmation of the discovery of 113.
Yoshii, Kenji; Hiramitsu, Yusuke*; Yoneda, Yasuhiro; Okajima, Yuka; Nishihata, Yasuo; Mizuki, Junichiro; Ikeda, Naoshi*
Ferroelectrics, 379(1), p.183 - 190, 2009/05
Times Cited Count:9 Percentile:39.82(Materials Science, Multidisciplinary)The magnetic and dielectric properties of perovskite manganites RCaMnO (R=Eu-Lu) have been investigated. Their dielectric constants were about 1000 at around room temperature. Inflections or peaks of temperature dependences of the dielectric constants were observed at around the charge-ordering temperatures determined from the magnetic measurements. Analyses of tan and EXAFS spectra suggested that the dielectric properties of this system are due to a spatial arrangement and transfer of the Mn-3d electrons. The observation of a two-peak structure of tan indicates that dielectric measurement can be used to observe homogeneity or in homogeneity of sample, as mentioned in our previous paper.
Hayakawa, Hironori*; Morimoto, Masanori*; Ikeda, Naoshi*; Yoneda, Yasuhiro; Kohara, Shinji*; Yoshii, Kenji; Matsuo, Yoji*; Michiuchi, Takamasa*; Mori, Shigeo*
Transactions of the Materials Research Society of Japan, 34(1), p.51 - 54, 2009/05
We have recently reported that LuFeO becomes ferroelectric below 330 K, owing to a charge-ordering transition of Fe ions. As details of the properties of this material have not been reported so far, we have investigated its local structure in the ferromagnetic phase by means of synchrotron X-ray diffraction. The analysis of pair-distribution function showed the existence of displacement of Lu atoms; this structure is different from the average structure of this materials known thus far. This result encourages a detailed reinvestigation of crystal structure of LuFeO. We also show the results obtained from some other experimental methods, such as dielectric measurement and electron diffraction.
Yoneda, Yasuhiro; Yoshii, Kenji; Hayakawa, Hironori*; Ikeda, Naoshi*
Transactions of the Materials Research Society of Japan, 34(1), p.15 - 18, 2009/03
Recently, there has been considerable interest in the dielectric properties of the cubic perovskite CaCuTiO. The material has shown to have high and relatively temperature independent dielectric permittivity over a wide temperature range from 100 to 600 K. Below 100 K the permittivity drops by almost three orders of magnitude, but is not accompanied by a structural phase transition. We studied CaCuTiO hoping to find signatures of local structural distortions that may explain the observe anomalies in the dielectric properties. Experiments were carried out using synchrotron radiation at several temperatures between room temperature and 10 K. Reconsideration is necessary for interpreting a huge permittivity by the local disorder model.
Morimoto, Koji*; Morita, Kosuke*; Kaji, Daiya*; Akiyama, Takahiro*; Goto, Shinichi*; Haba, Hiromitsu*; Ideguchi, Eiji*; Katori, Kenji*; Koura, Hiroyuki; Kudo, Hisaaki*; et al.
RIKEN Accelerator Progress Report, Vol.42, P. 15, 2009/00
In 2003-2007, we had performed an experiment to synthesize an element 113 by a Bi Zn reaction using a gas-filled recoil ion separator (GARIS) at RIKEN Nishina-Center. In a total of 241 days of net irradiation time experiment, two decay chains were observed and assigned from an isotope 113. The cross section of the Bi(Zn,n)113 reaction was determined to be 31 fb at that time. In order to increase the statistics of the decay property, we continued to produce more decay chains. The experiment was carried out from January 7 to March 31, 2008. The experimental conditions were identical to those used in the previous experiment. Zn ion beam of 353 MeV was extracted from RILAC. The net irradiation time was 83 days and the total dose of Zn was 2.28. In the present expriment any candidate of 113 was not observed. Then combining the results of the present and previous experiments, the production cross section of 113 was determined to be 22 fb.